A156028 -id:A156028 - cp's OEIS frontend

A155129 Decimal expansion of log_21 (19).

9, 6, 7, 1, 2, 6, 7, 1, 3, 4, 3, 2, 3, 3, 0, 2, 5, 9, 0, 8, 6, 2, 2, 5, 2, 7, 0, 3, 1, 0, 3, 6, 4, 0, 6, 2, 1, 0, 6, 9, 6, 6, 3, 3, 3, 3, 9, 8, 2, 2, 3, 0, 6, 7, 6, 7, 7, 4, 6, 7, 4, 0, 8, 2, 2, 0, 0, 3, 0, 1, 3, 5, 7, 6, 5, 0, 8, 3, 9, 1, 6, 0, 7, 3, 2, 9, 0, 3, 4, 8, 9, 7, 1, 3, 9, 6, 1, 2, 3

Offset: 0

N. J. A. Sloane, Oct 30 2009

			.96712671343233025908622527031036406210696633339822306767746...

Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for transcendental numbers

Cf. decimal expansion of log_21(m): A152825 (m=2), A153097 (m=3), A153131 (m=4), A153455 (m=5), A153611 (m=6), A153632 (m=7), A153895 (m=8), A154020 (m=9), A154171 (m=10), A154192 (m=11), A154213 (m=12), A154434 (m=13), A154499 (m=14), A154707 (m=15), A154839 (m=16), A154901 (m=17), A154977 (m=18), this sequence, A155532 (m=20), A155790 (m=22), A155909 (m=23), A156028 (m=24).

RealDigits[Log[21, 19], 10, 120][[1]] (* Harvey P. Dale, Dec 11 2012 *)

A155790 Decimal expansion of log_21 (22).

Original entry on oeis.org

1, 0, 1, 5, 2, 7, 9, 9, 0, 5, 6, 6, 2, 2, 0, 9, 1, 2, 4, 2, 7, 3, 9, 5, 4, 5, 4, 2, 8, 6, 8, 7, 9, 3, 2, 9, 0, 1, 4, 3, 6, 9, 9, 0, 4, 1, 0, 0, 7, 9, 0, 9, 4, 6, 2, 2, 5, 2, 0, 3, 6, 6, 9, 8, 1, 4, 0, 8, 7, 7, 9, 5, 7, 1, 6, 7, 7, 1, 3, 0, 8, 2, 1, 6, 7, 6, 1, 4, 9, 6, 1, 0, 2, 8, 2, 2, 4, 2, 4

Offset: 1

N. J. A. Sloane, Oct 30 2009

			1.0152799056622091242739545428687932901436990410079094622520...

Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index entries for transcendental numbers

Cf. decimal expansion of log_21(m): A152825 (m=2), A153097 (m=3), A153131 (m=4), A153455 (m=5), A153611 (m=6), A153632 (m=7), A153895 (m=8), A154020 (m=9), A154171 (m=10), A154192 (m=11), A154213 (m=12), A154434 (m=13), A154499 (m=14), A154707 (m=15), A154839 (m=16), A154901 (m=17), A154977 (m=18), A155129 (m=19), A155532 (m=20), this sequence, A155909 (m=23), A156028 (m=24).

RealDigits[Log[21, 22], 10, 100][[1]] (* Vincenzo Librandi, Sep 08 2013 *)

A157483 Numbers k such that k-1 and k+1 are divisible by exactly 3 primes, counted with multiplicity.

Original entry on oeis.org

19, 29, 43, 51, 67, 69, 77, 115, 171, 173, 187, 189, 237, 243, 245, 267, 274, 283, 285, 291, 317, 344, 355, 386, 403, 405, 411, 424, 427, 429, 435, 437, 476, 507, 597, 603, 604, 605, 638, 653, 664, 669, 723, 763, 776, 787, 789, 846, 891, 893, 907, 926, 963

Offset: 1

Vladimir Joseph Stephan Orlovsky, Mar 01 2009

nonn

Omega(a(n) - 1) = Omega(a(n) + 1) = 3, where Omega(n)=A001222(n). In general twin k-almost prime pairs are defined by Omega(a(n) - 1) = Omega(a(n) + 1) = k. Twin 1-almost primes are twin prime pairs (A014574). - Redjan Shabani, Jul 20 2012

			19 is a term: 19-1 = 18 = 2*3*3 and 19+1 = 20 = 2*2*5.

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Cf. A124936, A014612, A156028.

with(numtheory); a := proc (n) if bigomega(n-1) = 3 and bigomega(n+1) = 3 then n else end if end proc: seq(a(n), n = 2 .. 1100); # Emeric Deutsch, Mar 03 2009

q=3;lst={};Do[If[Plus@@Last/@FactorInteger[n-1]==q&&Plus@@Last/@FactorInteger[n+1]==q,AppendTo[lst,n]],{n,7!}];lst
Mean/@SequencePosition[PrimeOmega[Range[1000]],{3,,3}] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale, Mar 21 2020 *)

is(n)=bigomega(n-1)==3 && bigomega(n+1)==3 \\ Charles R Greathouse IV, Feb 05 2017

More terms from Emeric Deutsch, Mar 03 2009

cp's OEIS Frontend

A155129 Decimal expansion of log_21 (19).

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A155790 Decimal expansion of log_21 (22).

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A157483 Numbers k such that k-1 and k+1 are divisible by exactly 3 primes, counted with multiplicity.

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